Camera with cam-operated mirror driving mechanism

ABSTRACT

A camera includes a movable mirror arranged to be movable between a finder-viewing position and an exposure-retracted position, a spring member for applying to the movable mirror a force which causes the movable mirror to move from the finder-viewing position to the exposure-retracted position, and a movement mechanism for causing the movable mirror to move. The movement mechanism is provided with a cam member arranged to be rotated by a drive source and a cam follower arranged in abutment with the cam member. During rotation of the cam follower in a first direction, the movement mechanism causes the movable mirror to move toward the exposure-retracted position by means of the urging force of the spring member and, during rotation of the cam follower in a second direction, causes the movable mirror to move toward the finder-viewing position against the urging force of the spring member. The camera also includes a submirror arranged to be movable with respect to the movable mirror, the submirror being located in a focus detecting position for reflecting subject light toward a focus detecting device when the movable mirror is located in the finder-viewing position. The submirror is interlockingly located in an exposure-retracted position when the movable mirror is located in the exposure-retracted position.

This application is a division of Ser. No. 08/145,675 filed Nov. 4,1993, now U.S. Pat. No. 5,408,290, which is a division of Ser. No.07/886,318 filed May 22, 1992, now U.S. Pat. No. 5,311,229, which is acontinuation of Ser. No. 07/650,866 filed Feb. 5, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera provided with a movablemirror.

2. Description of the Related Art

It is known that a conventional mirror driving mechanism for asingle-reflex camera makes use of a method of rotating a movable mirrorby utilizing the unidirectional operation of a motor, such as thatdisclosed in U.S. Pat. No. 4,864,336.

In this disclosed method, rotation of the movable mirror from anexposure-retracted position (hereinafter referred to as a "mirror-upposition") to a finder-viewing position (hereinafter referred to as a"mirror-down position") is effected by means of a spring force, whilerotation of the movable mirror from the mirror-down position to themirror-up position is effected by means of the driving force of themotor.

However, it has been found that a camera having the above-describedmirror driving mechanism involves a number of disadvantages.

One disadvantage is that, as the level of source voltage decreases withthe consumption of a battery used as a power source, the number ofrevolutions of the motor which is driven for moving up the movablemirror is reduced and the time period required to move the movablemirror to the mirror-up position lengthens. The result is an increase ina release time lag.

Another disadvantage pertains to a moving-subject predictive autofocusmode which has recently been developed as one kind of autofocus mode,such as that disclosed in U.S. patent application Ser. No. 259,783 filedon Oct. 19, 1988, now abandoned. In such an autofocus mode, although areduction in and the stabilization the release time lag are importantconsiderations, the use of the conventional mirror driving mechanismcannot necessarily meet these and considerations.

Another disadvantage resides in the detection of the timing when themovable mirror reaches the mirror-down position. In the conventionalmechanism, when a shutter charging operation is completed andenergization of a shutter charging motor is stopped, a distance-meteringoperation is started. As a result, it is difficult to improve the framespeed at which continuous shooting is carried out while an autofocusoperation is being performed. To cope with this disadvantage, the art ofdetecting through an exclusive detecting switch the completion of themirror-down operation of the movable mirror through an exclusivedetecting switch is known in Japanese Laid-Open Patent Application No.Sho 57-73725.

Another disadvantage is that, since a driving power for moving themovable mirror downward is obtained from the spring force, it isdifficult to suppress the bounds of the movable mirror which occur whenit reaches the mirror-down position.

More specifically, if the spring force is strengthened. A retainingforce for retaining the movable mirror in the mirror-down position mustbe strong. However, the speed at which the movable mirror strikes amirror stopper increases, with the result that bounds cannot besuppressed and impact noise increases.

If the spring force is weakened, the speed at which the movable mirrorstrikes the mirror stopper can be reduced, but the retaining force forretaining the movable mirror in the mirror-down position weakens. As aresult, no strong force for suppressing bounds can be obtained and along time will elapse until the bounds disappear.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a camera of the typein which a movable mirror is driven to move from a finder-viewingposition toward an exposure-retracted position by means of a springmember, and in which, while a cam is being rotated in one direction by amotor serving as a drive source, the movable mirror can be driven fromthe finder-viewing position toward the exposure-retracted position bythe urging force of the spring member and from the exposure-retractedposition toward the finder-viewing position against the urging force ofthe spring member, merely by providing rotational control over the motorin response to the position of engagement between the cam and a camfollower.

It is another object of the present invention to provide a camera inwhich the timing when a distance-metering operation is to be initiatedcan be made earlier by providing a movable mirror arranged to be movablebetween a finder-viewing position and an exposure-retracted position adetecting means for detecting the arrival of the movable mirror at adistance-metering position.

The above and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionof a preferred embodiment of the present invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 12(a), 12(b), 12(c) and 12(d) diagrammatically show oneembodiment of the present invention;

FIG. 1 is a side elevational view of a mirror driving mechanism, showinga mirror-down state;

FIG. 2 is a side elevational view of a movable mirror in the mirror-downstate;

FIGS. 3(a) and 3(b) are a plan view and a cross-sectional view of afirst lever, respectively;

FIGS. 3(c) and 3(d) are a plan view and a cross-sectional view of asecond lever, respectively;

FIG. 4 is a plan view of a detection pattern, showing the state ofsignal detection when the movable mirror rests in a mirror-downposition;

FIG. 5 is a side elevational view showing the state in which the movablemirror rests in a mirror-up position;

FIG. 6 is a plan view showing the state of signal detection when themovable mirror rests in the mirror-up position;

FIG. 7 is a side elevational view showing the state of the movablemirror when a mirror-down operation is completed;

FIG. 8 is a plan view showing the state of signal detection when themirror-down operation is completed;

FIG. 9 is a table showing the state of signal detection during theoperation of the camera;

FIG. 10 is a block diagram showing a control circuit for use in thepresent embodiment;

FIGS. 11A through 11M are timing charts showing the operational sequenceof the control circuit; and

FIGS. 12(d), 12(b), 12(c) and 12(a) are flowcharts showing the operationof the control circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described belowin detail with reference to the accompanying drawings.

FIG. 1 is a schematic side elevational view showing one embodiment of acamera according to the present invention, and shows a mirror-down state(finder-viewing position). A photographic lens L is disposed on themiddle left side of the drawing and, in the mirror-down state, subjectlight is, as viewed in FIG. 1, reflected upward from a movable mirrorand conducted to a viewfinder optical system (not shown).

A movable mirror (main mirror) 16 is housed in a mirror box (not shown)and pivotal shafts 16b projecting from both sides of the movable mirror16 are respectively supported for pivotal motion by bearing portions ofthe mirror box. The movable mirror 16 is pivotally movable about thepivotal shafts 16b between the shown mirror-down position and themirror-up position (exposure-retracted position) shown in FIG. 5, and isselectively positioned at the mirror-down position or the mirror-upposition by a corresponding stopper which will be described later. Themovable mirror 16 is provided with a driving pin 16a to which istransmitted the driving power required to move up and down the movablemirror 16, and the driving pin 16a extends through a slot (not shown)formed in one side face of the mirror box. Pivotal motion of the movablemirror 16 is accomplished by a second lever 12 (to be described later)which is arranged to engage with the driving pin 16a.

As shown in FIG. 2 on an enlarged scale, the movable mirror 16, when inthe mirror-down state, is held in the mirror-down position in abutmentwith the stopper 31, and a distance-metering submirror 25, which issupported for pivotal motion about a pivotal shaft 16c on the back-faceside of the movable mirror 16, is positioned in abutment with a stopper32. The central light rays of subject light, which are conducted intothe camera body through the photographic lens L along an optical axis30a, are divided into two groups of light rays traveling along twodifferent optical axes. One group of light rays is reflected by themovable mirror 16 and travels toward the viewfinder optical system alongan optical axis 30b, while the other group of light rays is transmittedthrough a half-mirror portion 26 provided in the movable mirror 16 andtravels along an optical axis 30c. The latter group of light rays, whichpasses through the half-mirror portion 26 and travels along the opticalaxis 30c, is totally reflected by a total reflection mirror 27 of thesubmirror 25 and conducted toward a distance-metering unit 28. Thedistance-metering unit 28 has a known construction with respect to whichvarious proposals have been made, and a detailed description thereof isomitted.

The submirror 25 is pivotably urged by the spring force of a spring 29which is supported by a spring hooking portion 16d of the movable mirror16. The spring 29 is fixed to the movable mirror 16 at one end and is,at the other end, maintained in abutment with an operating portion 25aof the submirror 25, thereby constituting a toggle mechanism. In thetoggle mechanism, when in the mirror-down position (a state in whichfocus detection is possible), the spring 29 urges the submirror 25 inthe counterclockwise direction as viewed in FIG. 2 and, when in themirror-up position, urges the submirror 25 in the clockwise directioninto abutment with the back face of the movable mirror 16. To implementsuch a toggling operation, a cam member (not shown) is needed, but anillustration and description thereof is omitted since the mechanism isknown. The stopper 31 for restricting the mirror-down position of thesubmirror 25 is made from a known adjustment mechanism utilizing, forexample, an eccentric pin, so as to make fine adjustment of themirror-down position of the submirror 25.

A mirror driving mechanism for driving the movable mirror 16 which isarranged in the above-described manner will be described below withreference to FIGS. 1 to 8.

The mirror driving mechanism includes a first lever 11 and a secondlever 12 which are formed into the configurations shown in FIGS. 3(a),3(b) and 3(c), 3(d), respectively. The axial opening of the second lever12 is fitted onto a supporting shaft 13, formed on one side face of themirror box, in such a manner that the second lever 12 is rotatable aboutthe supporting shaft 13. An axial opening 11a of the first lever 11 isfitted onto a shaft portion 12a, which surrounds the aforesaid axialopening of the second lever 12, in such a manner that the first lever 11is rotatable about the shaft portion 12a. In this arrangement, thelength of engagement of both levers 11 and 12 is increased so that eachof the first lever 11 and the second lever 12 can be pivotally supportedwith a minimum inclination due to a play. In addition, the first lever11 and the second lever 12, which is positioned at a location betweenthe first lever 11 and the movable mirror 16, are arranged pivotablywith respect to each other. A pulling spring 15 is supported at one endby a spring hooking portion 11d of the first lever 11 and, at the otherend, by a spring hooking portion 12b of the second lever 12. As viewedin FIG. 1, the pulling spring 15 urges the first lever 11 in thecounterclockwise direction and the second lever 12 in the clockwisedirection so that the first and second levers 11 and 12 are pulledtoward each other. An abutment portion 11e of the first lever 11 and anabutment portion 12c of the second lever 12 are held in abutment witheach other by the spring force of the pulling spring 15 so that therelative rotation between the first and second levers 11 and 12 isinhibited. The abutment portion 11e of the first lever 11 projectstoward the second lever 12 which is positioned at a location between thefirst lever 11 and the movable mirror 16, and the abutment portion 12cof the second lever 12 is shaped in section to have a height whichenables abutment with the abutment portion 11e. An inspection hole 11fis formed in the first lever 11 so that the state of abutment ornon-abutment of the abutment portions 11e and 12c can be inspected. Theinspection hole 11f is used for the purpose of overcharge inspectionwhich will be described later.

A first am portion 12d and a second arm portion 12e are formed at theend of the second lever 12 opposite to the shaft portion 12a so as toposition the driving pin 16a of the movable mirror 16 between theportions 12d and 12e. When in the mirror-down position shown in FIG. 1,the first arm portion 12d is placed in abutment with the driving pin 16ato inhibit clockwise rotation of the movable mirror 16. During amirror-up operation, as the second lever 12 rotates in thecounterclockwise direction integrally with the first lever 11, thesecond arm portion 12e moves in abutment with the driving pin 16a,causing the movable mirror 16 to rotate in the clockwise direction fromthe mirror-down position to the mirror-up position. When the movablemirror 16 is placed in the mirror-up position, if the second lever 12rotates in the clockwise direction, the first arm portion 12d moves inabutment with the driving pin 16a, causing the movable mirror 16 torotate in the counterclockwise direction.

The counterclockwise rotating force of the second lever 12 for causingthe movable mirror 16 to rotate from the mirror-down position to themirror-up position, is produced by the spring force of a mirror-upspring 14 whose opposite ends are supported respectively by a springhooking portion 11b of the first lever 11 and a spring hooking portion14a provided on one side face of the mirror box. The clockwise rotatingforce of the second lever 12 for causing the movable mirror 16 to rotatefrom the mirror-up position to the mirror-down position while chargingthe mirror-up spring 14, as well as the operation of releasing themovable mirror 16 which is held at the mirror-down position in a chargedstate, is provided by the relation between a mirror driving cam 8 of amotor-driven type which will be described below and a cam abutmentportion 11c of the first lever 11 which is maintained in abutment withthe cam 8.

Referring to FIG. 1, a motor is indicated by reference numeral 1, and agear 2 is fixed to the output shaft of the motor 1. A transmissionmechanism 3 is disposed to transmit the output of the gear 2 to a gear4. The transmission mechanism 3 may be constructed from, for example, aspeed reduction gear train. Since it is possible to easily constructsuch a gear train by combining two speed gears, explanation of itsconstruction is omitted. If a plurality of mechanisms are to be drivenby a single motor to achieve a space saving, etc. in the camera body,the transmission mechanism 3 may be utilized as a mechanism forswitching the direction of transmission of driving power in accordancewith whether the direction of motor rotation is forward or reverse.

The gear 4, which is fixed to the top end of a transmission shaft 5 asviewed in FIG. 1, transmits the rotary motion of the motor 1 to thetransmission shaft 5. A worm gear 6 is fixed to the bottom end of thetransmission shaft 5. The worm gear 6 is meshed with a helical gear 7having a rotary shaft supported by the mirror box, and as the motor 1runs in a predetermined direction, the helical gear 7 rotates only inthe counterclockwise direction indicated by the arrow shown on the same.

The mirror driving cam 8 having the shown configuration is fixed to theface of the helical gear 7 which is located on a side opposite to themovable mirror 16. The mirror driving cam 8 rotates in the samedirection together with the helical gear 7.

When in the mirror-down state shown in FIG. 1, the operation of themotor 1 is stopped, and the cam abutment portion 11c of the first lever11 is in abutment with a maximum-diameter portion 8a of the mirrordriving cam 8, the maximum-diameter portion 8a being shaped into apredetermined rounded form. Accordingly, the first lever 11 is inhibitedfrom rotating in the counterclockwise direction by the urging force ofthe mirror-up spring 14. As described above, the first lever 11 and thesecond lever 12 integrally rotate in a state wherein they are pulledtoward each other up to a predetermined phase angle by the pullingspring 15. The first arm portion 12d of the second lever 12 is broughtinto abutment with the driving pin 16a so as to position the movablemirror 16 in the mirror-down position immediately before the camabutment portion 11c comes into abutment with the maximum-diameterportion 8a of the mirror driving cam 8. The first lever 11 rotatesagainst the spring force of the pulling spring 15 in the clockwisedirection to a slight extent while overcharging the mirror-up spring 14until the cam abutment portion 11c reaches the maximum-diameter portion8a. The second lever 12 is subjected to the spring force of the pullingspring 15 to elastically press the movable mirror 16 against themirror-down position. This overcharged state can be inspected throughthe inspection hole 11f formed in the first lever 11. If a predeterminedgap is established between the abutment portions 11e and 12c of thelevers 11 and 12, it is determined that an effective overcharged statehas been achieved. If the abutment portions 11e and 12c are in contactwith each other or spaced apart beyond the predetermined gap, anadjustment is performed to obtain the predetermined gap.

The helical gear 7 is meshed with a shutter-charging helical gear 9 tocause it to rotate in the clockwise direction indicated by the shownarrow, thereby charging a shutter (not shown) in synchronization withthe driving of the movable mirror 16. A shutter charging cam 10 is fixedto the helical gear 9. A shutter charging lever 17 is arranged forpivotal motion about a pivotal shaft 17a, and a roller 18 is provided atone end of the shutter charging lever 17 and is supported for rotationabout a support shaft 17b. The roller 18 is in abutment with the camsurface of the shutter charging cam 10. A roller 19, which is rotatablysupported by a support shaft 17c provided at the other end of theshutter charging lever 17, is in abutment with a charge lever providedon the side of the shutter (not shown). The shutter charging lever 17 isarranged to charge the shutter (not shown) while rotating in thecounterclockwise direction. In FIG. 1, the shutter charging lever 17 isshown as holding the shutter in a completely charged state.

A position detecting mechanism for detecting the position of the mirrordriving cam 8 is disposed on the reverse face of the helical gear 7 incoaxial relation thereto. This mechanism is formed by a contact piece 20secured to the helical gear 7 and a board 21 having one surface providedwith detection patterns 22, 23 and 24 which are arranged for contactwith the contact piece 20.

FIG. 4 is an enlarged plan view of the board 21. The detection pattern22 is supplied with a ground potential through an input portion 22c, andthe ground potential is supplied to a signal pattern portion 22a througha connection portion 22b. The detection pattern 23 includes a signalpattern portion 23a, a connection portion 23b and an output portion 23c,and the detection pattern 24 includes signal pattern portions 24a and24b, a connection portion 24c and an output portion 24d. When in themirror-down position, the contact piece 20 is brought into contact withthe signal pattern portions 22a, 23a and 24a which are concentricallyspaced apart along a straight solid line representing a contact line20a, whereby it is determined whether the ground potential supplied fromthe detection pattern 22 is transmitted to the detection patterns 23 and24. In the following explanation, it is assumed that when the detectionpatterns 23 and 24 come into contact with the detection pattern 22, eachof the detection patterns 23 and 24 is set to a low (Lo) level; if notin contact with the detection pattern 22, each of the detection patterns23 and 24 is set to a high (Hi) level. Accordingly, if the signalpattern portions 22a, 23a and 24a are electrically connected as shown inFIG. 4 (corresponding to FIG. 1) and each of the detection patterns 23and 24 is at the low level, it is detected that the movable mirror 16 isplaced in the mirror-down position.

When in the mirror-down position shown in FIG. 1, counterclockwiserotation of the first lever 11 is inhibited owing to the abutmentbetween the maximum-diameter portion 8a and the cam abutment portion11c. In this state, the helical gear 7 initiates rotation. When thehelical gear 7 rotates by a small amount, the cam abutment portion 11cof the first lever 11 and the mirror driving cam 8 come out of abutmentwith each other, that is to say, the first lever 11 is allowed to freelyrotate. Accordingly, the first lever 11 is rotated in thecounterclockwise direction by the spring force of the mirror-up spring14 which is in a charged state. At this time, since the first lever 11and the second lever 12 are pulled toward each other by the pullingspring 15 and the abutment portions 11e and 12c are in abutment witheach other, the first lever 11 and the second lever 12 integrally rotatein the counterclockwise direction. Accordingly, the second arm portion12e of the second lever 12 comes into abutment with the driving pin 16aof the movable mirror 16 to cause the movable mirror 16 to rotate in theclockwise direction so as to rotate the movable mirror 16 from themirror-down position to the mirror-up position. As shown in FIGS. 3(c),3(d) and 5, a first cam surface 12f and a second cam surface 12g areformed on the surface of the second arm portion 12e which is broughtinto and out of abutment with the driving pin 16a. when the second lever12 in the mirror-down state initiates counterclockwise rotation, thefirst cam surface 12f having a projection-like configuration initiallycomes into abutment with the driving pin 16a to rotate the movablemirror 16 in the clockwise direction. When the second lever 12 furtherrotates and reaches the vicinity of the mirror-up position, the point ofabutment with the driving pin 16a travels from the first cam surface 12fto the second cam surface 12g. Immediately thereafter, when the movablemirror 16 comes into abutment with a stopper (not shown), the mirror-upoperation is completed. The second cam surface 12g has an angle whichserves to increase a retaining force for retaining the movable mirror 16in the mirror-up state, thereby preventing the movable mirror 16 frombounding at the mirror-up position when it has been moved there by theurging force of the mirror-up spring 14. Even in a case where it isimpossible to completely prevent the movable mirror 16 from boundingmerely by the retaining force produced by the second cam surface 12g,the first cam surface 12f acts to stop the movable mirror 16 with aminimum number of bounds, whereby it is possible to stabilize themovable mirror 16 at the mirror-up state within a short time.

When in the mirror-up state, the submirror 25 also rotates in thecounterclockwise direction (in a closing direction with respect to themovable mirror 16) by the above-described mechanism and, as shown inFIG. 5, comes into abutment with the back face of the movable mirror 16by the action of the spring 29.

After the aforesaid movable mirror 16 is released from retention, themotor 1 remains running and the helical gear 7 continues to rotate in apredetermined direction. However, when the state shown in FIG. 5 isreached and the mirror-up operation is completed, the motor 1 and thehelical gear 7 come to a temporary rest.

Referring to a shutter charging operation, since the roller 18 isdisengaged from the maximum-diameter portion of the shutter charging cam10, the shutter charging lever 17 is allowed to rotate in the clockwisedirection, while the roller 19 operates to release the shutter charginglever of the shutter (not shown) from its charged state. In theabove-described state, the shutter (not shown) is ready to initiate anexposure operation.

When the mirror-up operation is completed and the movable mirror 16rests in the mirror-up position, the position detecting mechanism forthe mirror driving cam 8 is placed in the signal detection state shownin FIG. 6.

As shown, the contact piece 20 makes contact with only the signalpattern 22a on the contact line 20a. Accordingly, the detection patterns23 and 24 are both at the high levels.

FIG. 7 is a view showing the state of completion of a mirror-downoperation during a shutter charging operation.

In an initial period of the mirror-down operation, the cam abutmentportion 11c of the first lever 11 comes into abutment with a cam portion8b of the mirror driving cam 8, thereby causing the first lever 11 andthe second lever 12 to rotate together in the clockwise direction. Thefirst arm portion 12d of the second lever 12 comes into abutment withthe driving pin 16a of the movable mirror 16, thereby causing themovable mirror 16 to rotate in the counterclockwise direction. When themotor 1 further runs, the cam abutment portion 11c of the first lever 11comes into abutment with the cam portion 8b of the mirror driving cam 8to cause the movable mirror 16 to rotate in the counterclockwisedirection to the mirror-down position where the movable mirror 16 isbrought into abutment with the stopper 31. FIG. 7 shows this mirror-downstate. In this state, the cam abutment portion 11c of the first lever 11is not in abutment with the maximum-diameter portion 8a of the mirrordriving cam 8. The motor 1 further runs to cause the first lever 11 torotate in the clockwise direction until the above-described overchargedstate is reached. When the overcharged state is reached, the camabutment portion 11c of the first lever 11 is, as shown in FIG. 1,brought into abutment with the maximum-diameter portion 8a of the mirrordriving cam 8, and the operation of the motor 1 is stopped. Adescription will be given later as to the state of energization of themotor 1 before the cam abutment portion 11c of the first lever 11 comesinto abutment with the maximum-diameter portion 8a of the mirror drivingcam 8.

Immediately after the movable mirror 16 has reached the mirror-downposition, the movable mirror 16 might bound by striking the stopper 31.However, since the first lever 11 is rotated to the overcharged positionagainst the spring force of the pulling spring 15, the second lever 12in engagement with the driving pin 16a of the movable mirror 16suppresses the bounds of the movable mirror 16 owing to the spring forceof the pulling spring 15. Accordingly, the movable mirror 16 settles atthe mirror-down position within a short time.

Meanwhile, in the shutter charging system, the shutter charging cam 10and the roller 18 comes into abutment with each other, so that theshutter charging lever 17 initiates rotating in the counterclockwisedirection. Basically, a mirror-down operation precedes a shuttercharging operation. However, as shown in FIG. 7, a plurality of drivingloads are overlapped so as to maintain an approximately uniform loadwithin a range in which a maximum load does not increase.

FIG. 8 shows the state of signal detection which is carried out by theposition detecting mechanism for the mirror driving cam 8 uponcompletion of a mirror-down operation. The signal pattern portions 22aand 24b are in contact with the contact line 20a of the contact piece20, and the detection pattern 23 is at the high level, while thedetection pattern 24 is at the low level.

FIG. 9 is a table showing the signal detection state of the detectionpatterns 23 and 24 in each step of one rotation of the mirror drivingcam 8.

In a state wherein a shutter charging operation is completed and theoperation of the mechanism is stopped as shown in FIGS. 1 and 4, each ofthe detection patterns 23 and 24 is at the low level as described above.In this state, energization of the motor 1 is initiated, and thedetection pattern 23 is switched from the low level to the high level inthe phase where the cam abutment portion 11c of the first lever 11 isreleased from the maximum-diameter portion 8a of the mirror driving cam8. In this phase, the movable mirror 16 starts to move up by virtue ofthe mirror-up spring 14 and stabilizes at the mirror-up position in apredetermined time. In other words, by setting a predetermined timer atthe timing when the detection pattern 23 is switched from the low levelto the high level, it is possible to detect the timing of stabilizationof the movable mirror 16 at the mirror-up position, irrespective of thestate of an electrical power source.

During the above-described operation, the energization of the motor 1 iscontinued, and the detection pattern 24 is switched from the low levelto the high level in the phase where the roller 18 of the shuttercharging system is released from the state of being restricted by theshutter charging cam 10. At this point in time, the energization of themotor 1 is stopped and the motor 1 is braked by short-circuiting itsterminals, whereby each mechanism comes to rest in the state shown inFIG. 5.

After completion of the exposure operation, when energization of themotor 1 is initiated and the state shown in FIG. 7 is reached, thesignal of the detection pattern 24 is switched from the high level tothe low level. According to this signal, it is possible to accuratelydetect the timing when the movable mirror 16 and the submirror 25 reachthe mirror-down position, irrespective of the state of the electricalpower source. In addition, by setting a predetermined timer on the basisof such timing, it is possible to accurately detect the timing when themovable mirror 16 and the submirror 25 stabilize. Although, during theenergization of the motor 1, the detection pattern 24 switches from thelow level to the high level, the energization of the motor 1 iscontinued. When the roller 18 reaches the maximum-diameter portion ofthe shutter charging cam 10, the detection pattern 23 switches from thehigh level to the low level by means of the signal pattern portion 23a.When the shutter charging cam 10 further rotates by a predeterminedangle, the detection pattern 24 switches from the high level to the lowlevel by means of the signal pattern portion 24a. The above-describedsignal-level change is utilized so that the timing when the energizationof the motor 1 is stopped and its terminals are short-circuited to brakethe motor 1 to bring the mirror driving cam 8 to rest in the state ofFIG. 1 can be set as two different times: an earlier time and a latertime.

If the source voltage is high, the speed of revolution of the motor 1 isfast and the amount of overrunning of the mirror driving cam 8 afterbraking is large. For this reason, the motor 1 is braked at an earliertime during the process of the signal-level change of the detectionpattern 23 from the high level to the low level, thereby bringing themirror driving cam 8 to rest at the predetermined position shown in FIG.1.

If the source voltage is low, the speed of revolution off the motor 1 isslow and the amount of overrunning of the mirror driving cam 8 afterbraking is small. For this reason, the motor 1 is braked at a later timeduring the process of the signal-level change of the detection pattern23 from the high level to the low level, thereby bringing the mirrordriving cam 8 to rest at the predetermined position shown in FIG. 1.

Although, in the presently preferred embodiment, switching between thebraking timings is performed at two different times only, it is a matterof course that if such switching is performed at shorter intervals, amore accurate stop phase can be obtained. Accordingly, the time periodfrom the moment for initiating energization of the motor 1 until themoment for initiating a mirror-up operation can be kept shorter andstabler for variations in the source voltage.

As described above, with the present embodiment, it is possible torealize a reduction in and the stabilization of a release time lag andalso an arrangement which makes it possible to accurately detect thetiming of stabilization of the movable mirror 16 at the mirror-upposition. Accordingly, the present embodiment is advantageous forincreasing the frame speed of continuous shooting in a flying releasesystem such as that disclosed in U.S. Pat. No. 4,679,925.

FIG. 10 is a block diagram showing one example of the control circuitused in the presently preferred embodiment.

The shown control circuit is provided with a light-metering switch 100which is turned on at the first stroke of a release button (not shown),and a release switch 101 which is turned on at the second stroke of therelease button. Signals from the switches 100 and 101 are inputted to amicroprocessor (MPU) 102. The MPU 102 also receives a shutter-runningcompletion signal 103 from a means for detecting the completion ofrunning of the shutter trailing curtain, signals from the detectionpatterns 23 and 24 for controlling energization of the motor 1, and afilm advance signal 104 from a film advance detecting means (not shown).A light-metering circuit 105 and a distance-metering circuit 106 aresupplied with operational-timing information by the MPU 102, andtransmit individual outputs to the MPU 102. The motor 1 and a filmtransporting motor 107 are driven by signals supplied from the MPU 102through motor drivers 108 and 109, respectively. The motor drivers 108and 109 have bridge circuits which can switch the states of therespective motors 1 and 107 between a forward or reverse energized stateand an electrically braked state utilizing a short circuit. When theshutter is to be activated, a shutter leading-curtain magnet 110 isenergized in response to a signal from the MPU 102 to start running of aleading curtain. After the duration of a predetermined shutter speed haspassed, a shutter trailing-curtain magnet 111 is energized in responseto a signal from the MPU 101 to start running of a trailing curtain. Aninterface for connecting a photographic lens and a camera body, neitherof which is shown, is realized not by a mechanical coupling but byelectrical communication between the MPU 102 of the camera body and alens controlling circuit 112. Electrical power for driving thephotographic lens is supplied from the camera body.

The photographic lens includes a diaphragm driving actuator 113 and afocus driving actuator 114. The diaphragm driving actuator 113 and thefocus driving actuator 114 are driven by means of a lens controllingcircuit 112 in response to driving timings specified by the MPU 102.

The control circuit having the above-described arrangement andconstruction operates in accordance with the timing charts shown inFIGS. 11A through 11M.

These timing charts illustrates the state in which the release switch101 is turned on at the second stroke and connected in the on state,with the light-metering switch 100 relative to the first stroke of therelease button (not shown) remaining in the on state. Acontinuous-shooting mode and a single-shooting mode can be selectivelyset as a film transporting mode by a mode setting means (not shown), andthe timing charts show a state corresponding to the setting of thecontinuous-shooting mode. A battery check is accomplished by checking anactual load while electricity is being supplied to the leading-curtainmagnet 110 and the trailing-curtain magnet 111 of the shutter. In thetiming charts, there is shown a state in which the movable mirror 16changes its state while moving up and down. The timing charts also showa state in which continuous shooting is effected by performing autofocuswhile predicting the movement of a moving subject.

The operation of the present preferred embodiment of the camera will bedescribed below with reference to the timing charts of FIGS. 11A through11M as well as the flowcharts shown in FIGS. 12(a) to 12(d).

When a power switch (not shown) is turned on (Step S1) and thelight-metering switch 100 is turned on (Step S2), a wake-up operation isperformed (Step S3) to activate a DC/DC converter (not shown), therebyactivating individual circuits.

Then, the light-metering circuit 105 and the distance-metering circuit106 are activated (Step S4), and the focus driving actuator 114 of thephotographic lens is activated on the basis of the information providedby the light-metering circuit 105 and the distance-metering circuit 106,thereby initiating driving for lens focusing (Step S5). The manner ofdistance metering and driving for lens focusing in the embodiment issimilar to that disclosed in detail in U.S. patent application Ser. No.259,783 filed on Oct. 19, 1988 (abandoned in favor of Ser. No. 519,251now U.S. Pat. No. 5,012,267), i.e., driving for lens focusing isperformed while predicting the movement of a moving subject. Explanationthereof is omitted for the sake of simplicity.

If it is determined in Step S6 that the release switch 101 is not on,the process proceeds to Step S7, where a predetermined amount of drivingfor lens focusing is performed. Then, the process returns to Step S4,where a light•distance-metering operation is performed. If the releaseswitch is turned on during this time, the driving for lens focusing isstopped (Step S8) and the process enters a photographic sequence.

In the present preferred embodiment, driving for lens focusing isstopped halfway in order to mainly cope with a release time lag whichmay occur after the release switch 101 has been turned on. However,after a predetermined amount of lens driving has been performed, theprocess may be allowed to enter the photographic sequence. Otherwise,the process may be inhibited from proceeding to the photographicsequence on the basis of the state of a distance-metering operation.

In Step S9, a battery check is performed. If the battery voltage ishigher than a predetermined voltage, a BCHi flag is set up (Step S10).If the battery voltage is lower than the predetermined voltage, a BCLoflag is set up (Step S11).

In Step S12, energization of the motor 1 is initiated. At the same time,a release-time-lag stabilizing 70-ms timer for maintaining a constantrelease time is started (Step S13). The interval of this timer is set onthe basis of the maximum period required for lens-diaphragm drivingwhose period varies with an aperture value. In addition, the interval isselected to be the duration it takes for the movable mirror 16 tocomplete its mirror-up operation. Accordingly, it is possible to keepconstant a release time lag which may occur during the execution of theabove noted and moving-subject predictive autofocus, whereby predictionaccuracy is improved.

To prevent a rush current from occurring at the mime of activation ofthe motor 1, when a time delay of 15 milliseconds passes (Step 14), theoperation of stopping down a lens aperture is started (Step S15).

If the detection pattern 23 for detecting the phase of the mirrordriving cam 8 switches to its high level in Step S16, a mirror-up-stateassurance 35-ms timer is started (Step S17). The timing at which thedetection pattern 23 switches to the high level corresponds to the phasewhere the movable mirror 16 starts to move up.

The energization of the motor 1 is continued, and when the signal of thedetection pattern 24 switches to its high level, the energization of themotor 1 is stopped (Step S18) and electrical braking is applied to bemotor 1 (Step).

If the lens aperture is stopped down (Step S20), when the conditions ofthe mirror-up-state assurance 35-ms timer and the release-time-lagstabilizing 70-ms timer are satisfied (Steps S21 and S22), energizationof the shutter leading-curtain magnet 110 is performed (Step S23). Whenthe duration of a predetermined shutter speed has passed (Step S24),energization of the shutter trailing-curtain magnet 111 is performed(Step S25) to cause the shutter leading and trailing curtains to run,thereby effecting an exposure operation.

When a shutter-running completion signal is inputted in Step S26,energization of the motor 1 is started (Step S27). When a time delay of15 milliseconds passes Step S28), the operation of opening the lensaperture is initiated (Step S29).

When the operation of opening the lens aperture is completed in StepS30, energization of the film transporting motor 107 is initiated tostart film winding (Step S31).

When the signal of the detection pattern 24 switches to its low level inStep S32, a mirror-down-position stabilizing 40-ms timer is started(Step S33). This timer serves to ensure that small vibrations remainingafter the movable mirror 16 and the submirror 25 have reached themirror-down position are stopped.

If the continuous-shooting mode is selected (Step S34), distance- andlight-metering operations are initiated (Step S35). If thesingle-shooting mode is selected, the process proceeds to Step S36.

If the BC flag memorized in Step S10 or S11 is at the high level whenthe detection pattern 23 has switched to the low level (Step S36),electrical braking is immediately applied to the motor 1 (Step S39). Ifthe BC flag memorized in Step S10 or S11 is at the low level when thedetection pattern 23 has switched to the low level (Step S36), after thedetection pattern 24 has switched to the low level (Step S38),electrical braking is applied to the motor 1 (Step S39).

When the completion of film winding is detected in response to a filmwinding signal in Step S40, the energization of the film transportingmotor 107 is stopped and electrical braking is applied to the motor 107(Step S41).

If the continuous-shooting mode is selected in Step 42, the processproceeds to Step S43. If the release switch 101 is on in Step S43, theprocess proceeds to Step S44; if it is off, the process returns to StepS2.

If it is determined in Step S44 that the distance- and light-meteringoperations have been completed, driving for lens focusing is initiated(Step S45). After a time delay of 15 milliseconds has passed (Step 47),energization of the motor 1 is initiated (Step S47) and therelease-time-lag stabilizing 70-ms timer is started (Step S48).

Then, when a time delay of 15 milliseconds passes (Step 49), theoperation of stopping down the lens aperture is started (Step S50).

When the signal of the detection pattern 23 switches to the high level(Step S51), the mirror-up-state assurance 35-ms timer is started (StepS52). When the signal of the detection pattern 24 switches to the highlevel (Step S53), the energization of the motor 1 is stopped andelectrical braking is applied to the motor 1 (Step S54).

When the operation of stopping down the lens aperture is completed (StepS55), the process proceeds to Step 56, where the driving for lensfocusing is completed. When the mirror-up-state assurance 35-ms timertimes out (Step S57), it is detected in Step S58 whether therelease-time-lag stabilizing 70-ms timer has timed out. If it isdetected that the 70-ms timer has timed out, the process returns to StepS23, where energization of the shutter leading curtain magnet 110 isperformed. Subsequently, a similar sequence of operations is performedin accordance with the aforesaid flow. If the release switch 101 remainson with the continuous-shooting mode selected, photography is continuedin accordance with the aforesaid flow.

As is apparent from the foregoing, in accordance with the presentpreferred embodiment, since the mirror-up operation of the movablemirror utilizes the spring force of the spring member, it is possible tominimize the time domain of a mirror-up time period which varies withthe rotational speed of the motor. In addition, without a specialactuator, it is possible to minimize variations in the mirror-up timeperiod due to changes in a source voltage, whereby a release time lagcan be reduced and stabilized.

In accordance with the above-described embodiment, since there areprovided a plurality of motor-energization stop phases for themirror-down operation of the movable mirror, it is possible to alter abraking position in accordance with variations in the rotational speedof the motor, whereby the stop phase of the cam member can bestabilized.

Accordingly, by selecting a suitable energization stop phase withrespect to a variation in the source voltage of the motor, it ispossible to reduce variations in the duration of a mirror-up operation,whereby a release time lag can be reduced and stabilized.

In accordance with the above-described embodiment, during the operationof the driving motor, it is possible to detect that the submirrorserving as a distance-metering mirror has reached a distance-meteringposition (the mirror-down position shown in FIG. 1). Accordingly, evenif the time required to drive the submirror to its down position varieswith variations in the source voltage, it is possible to accuratelydetect the timing of stabilization of the submirror in thedistance-metering position, whereby a distance-metering operation can beexecuted after the submirror has stabilized. In addition, it is possibleto start a distance-metering operation at an earlier time even in thedriving sequence of stopping the motor after completion of a shuttercharging operation.

The submirror is driven toward the distance-metering position by themotor, and an overcharge is absorbed by means of a second spring memberwhen the submirror comes to rest at the distance-metering position. Ifthe spring force of a first spring member for driving the submirrortoward the exposure-retracted position is strongly set, it is possibleto minimize the bounds of the submirror which may occur in thedistance-metering position as a result of a mirror driving operation. Inaddition, no large impact noise is produced at the distance-meteringposition by the mirror driving operation.

What is claimed is:
 1. A camera comprising:(a) a movable mirror arrangedto be movable between a finder-viewing position and anexposure-retracted position; (b) a spring member for applying to saidmovable mirror a force which causes said movable mirror to move fromsaid finder-viewing position to said exposure-retracted position; (c) amovement mechanism for causing said movable mirror to move, saidmovement mechanism including a cam member arranged to be rotated by adrive source and a cam follower arranged in abutment with said cammember, said movement mechanism, during motion of said cam follower in afirst direction, causing said movable mirror to move toward saidexposure-retracted position by means of the urging force of said springmember and, during motion of said cam follower in a second direction,causing said movable mirror to move toward said finder-viewing positionagainst the urging force of said spring member; and (d) a submirrorarranged to be movable with respect to said movable mirror, saidsubmirror being located in a focus detecting position for reflectingsubject light toward a focus detecting device when said movable mirroris located in said finder-viewing position, and said submirror beinginterlockingly located in an exposure-retracted position when saidmovable mirror is located in said exposure-retracted position.
 2. Acamera according to claim 1, wherein said movable mirror is pivotallysupported.
 3. A camera according to claim 1, wherein said cam followerof said movement mechanism includes a first lever arranged in abutmentwith said cam member and a second lever interlocked with said movablemirror, said first and second levers being supported about a common axisand being arranged to be pulled toward each other by a second springmember.
 4. A camera according to claim 3, wherein said cam member isconfigured to bring about a cam displacement which permits said movablemirror to be forced against a stopper by the urging force of said secondspring member upon completion of driving of said movable mirror towardsaid finder-viewing position.
 5. A camera according to claim 1, furthercomprising phase detecting means for detecting a predetermined phase ofsaid cam member.
 6. A camera according to claim 5, wherein said drivesource of said movement mechanism is a motor, the rotation of which iscontrolled on the basis of detection information provided by said phasedetecting means.
 7. A camera according to claim 1, wherein said springmember is charged in interlocked relation to the movement of saidmovable mirror from said exposure-retracted position to saidfinder-viewing position.
 8. A camera according to claim 1, wherein saidsubmirror is moved by a toggle spring mechanism which switches itsurging direction in interlocked relation to the movement of said movablemirror, so that said submirror moves between said focus detectingposition and said exposure-retracted position in interlocked relation tothe movement of said movable mirror.
 9. A camera comprising:(a) amovable mirror arranged to be movable between a focus detecting positionand an exposure-retracted position; (b) a focus detecting devicearranged to receive subject light reflected by said movable mirror whensaid movable mirror is located in said focus detecting position; (c) aspring member for applying to said movable mirror a force which causessaid movable mirror to move from said focus detecting position to saidexposure-retracted position as well as a force which causes said movablemirror to move from said exposure-retracted position to said focusdetecting position; and (d) a movement mechanism for causing saidmovable mirror to move, said movement mechanism including a cam memberarranged to be rotated by a drive source and a cam follower arranged inabutment with said cam member, said movement mechanism, during motion ofsaid cam follower in a first direction, causing said movable mirror tomove toward said exposure-retracted position by means of the urgingforce of said spring member and, during motion of said cam follower in asecond direction, causing said movable mirror to move toward said focusdetecting position against the urging force of said spring member.
 10. Acamera according to claim 9, wherein said movable mirror is pivotallysupported.
 11. A camera according to claim 9, wherein said cam followerof said movement mechanism includes a first lever arranged in abutmentwith said cam member and a second lever interlocked with said movablemirror, said first and second levers being supported about a common axisand being arranged to be pulled toward each other by a second springmember.
 12. A camera according to claim 9, further comprising phasedetecting means for detecting a predetermined phase of said cam member.13. A camera according to claim 12, wherein said drive source of saidmovement mechanism is a motor, the rotation which is controlled on thebasis of detection information provided by said phase detecting means.